JPA中具有多对多关系的三个连接表查询[关闭]

Question

共有三个表：Hospital、Medical_Service和Language_Service， 医院可提供医疗服务和语言服务。所以有两个多对多关系。

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现在我想通过三个条件搜索医院：Postcode，Medical，Language，这个SQL怎么写。

Answer 1

我认为您的 SQL 可能看起来像这样：

SELECT * FROM Hospital WHERE Postcode = 3000 AND
Hospital_id IN
    (SELECT Hospital_id FROM Hospital_Medical hm
    INNER JOIN Medical_Service m ON hm.Medical_id = m.Medical_id
    where Medical_name = 'Emergency') AND
Hospital_id IN
(SELECT Hospital_id FROM Hospital_Language hl
    INNER JOIN Language_Service l ON hl.Language_id = l.Language_id
    where Language_name = 'English')

Answer 2

应该是这样的：

SELECT h 
FROM Hospital h JOIN h.medicalService m JOIN h.languageService l
WHERE h.postcode = :postCodeParameter 
AND m.medicalName = :medicalNameParameter 
AND l.languageName = :languageNameParameter

假设您的实体映射正确。 HM_id 和 HL_id 列也是不必要的，应该加入主键。